Abstract
We presented the unusual result of photobleaching (PB) in Ge-deficient Ge16.8Se83.2 thin films with continuous irradiation with 560 nm laser for 12000 s, which is contradicted with the previous reports that the PB only occurs in GexSe100-x films with x > 30. Observation of the dynamics variations of the photo-induced effects indicated that, photodarkening (PD) appears almost instantaneously upon light irradiation, saturates faster in a shorter time scale, and then photobleaching (PB) becomes dominant. Moreover, both PD and PB process accelerates with increasing irradiation power density. Raman spectra provided the evidence on the change of the photostructure of the samples, e.g. the structural transformation from Ge(Se1/2)4 edge-sharing (ES) to corner-sharing (CS) tetrahedral and homopolar Ge-Ge and Se-Se bonds to heteropolar Ge-Se bonds.
Highlights
Photodarkening (PD) and photobleaching (PB) effects, defined as a red or blue shift in an optical absorption edge, respectively[1,2], are useful for a variety of applications such as information storage, optical switching and so on[3,4,5]
The X-ray Diffraction (XRD) patterns indicated that the as-deposited films are amorphous
We have demonstrated that coexistence of fast PD and slow PB in Ge-deficient chalcogenide glassy thin films, and observed that the degrees of PD and PB processes are directly related to the irradiation power density
Summary
Photodarkening (PD) and photobleaching (PB) effects, defined as a red or blue shift in an optical absorption edge, respectively[1,2], are useful for a variety of applications such as information storage, optical switching and so on[3,4,5]. Su et al investigated the photosensitivity of GexAsySe1-x-y system, and found that optically stable composition can only exist in the glasses with a mean coordination number of around 2.45 in GexAsySe1-x-y12. In the present paper, we reported that, with continuous irradiation, PD appears almost instantaneously upon light irradiation, and saturates faster in a shorter time scale, and PB becomes dominant at a long time scale Such an unexpected PB behavior in Ge-deficient Ge16.8Se83.2 films was subsequently assigned to the structural transformation from ES-Ge(Se1/2)[4] tetrahedral convert to CS-Ge(Se1/2)[4] tetrahedral units upon irradiation and homopolar Ge-Ge and Se-Se bonds to heteropolar Ge-Se bonds
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